ABSTRACT
Chapter 9, prepared in six sections, addresses the thermal response of a PWR pressurizer to plant transients. The pressurizer structure, function and associated components for water level and pressure control including electric heaters, spray, and safety and relief valves are described. Also described are the chemical and volume control system and the quench tank. A mathematical model is developed for a multiregion pressurizer by applying the continuity and energy equations to each region and closing the set of equations by the volume constraint. The set of equations is solved explicitly for the state variables of specific enthalpies and pressure. The constitutive equations required for the solution are discussed, including critical flow at the valves, condensation on the wall and processes at the bulk liquid-bulk vapor. The TMI accident, which was exacerbated by the stuck open PORV, is discussed in the context of pipe break size classification. Finally, the procedure to calculate the required hole size (valve flow area) for the primary system depressurization is presented.
